Neuropathy of the lateral

cutaneous nerve of the forearm Manohar ARUMUGAM,1 Shariful HASAN (Malaysia),2 Gowreesan ARIARATNAM,1

1 Department of Orthopaedic Surgery and 2 Department of Medicine, Faculty of Medi-

cine and Health Science, Universiti Putra Malaysia, Malaysia

ABSTRACT

Entrapment of the lateral cutaneous nerve of the forearm is a relatively uncommon condition. It is one

of the differential diagnosis of pain at the elbow and paraesthesia of the distal forearm specifically the

anterolateral area of the forearm. This case study describes neuropathy involving the lateral cutaneous

of the forearm, which occurred in a 50-year-old lady with no history of previous upper limb trauma.

Keywords: Neuropathy, lateral cutaneous nerve of the forearm, neurpraxia

INTRODUCTION

The lateral cutaneous nerve of the forearm

(LCNF) is a sensory nerve. It is the terminal

branch of the musculocutaneous nerve and is

also known as the lateral antebrachial cuta-

neous nerve. 1 It provides sensory innerva-

tion to the anterolateral aspect of the fore-

arm. It traverses the anterior compartment of

the arm anterolaterally between the biceps

and brachialis. It exits the arm two to five

centimetre proximal to the elbow flexion

crease lateral to the biceps tendon by pierc-

ing the brachial fascia. It is at this point that

the LCNF gets entrapped. 1, 2 The nerve then

runs volar to the cephalic vein, as it travels

down the forearm to the wrist along its radial

border. At the wrist, the nerve is located vo-

lar to the radial artery and then runs distally

towards the ball of the thumb.

Case Report

Correspondence author: Manohar ARUMUGAM

Department of Orthopaedic Surgery, Faculty of Medicine and Health Science, Universiti Putra

Malaysia, Jalan Puchong, 43400, Serdang, Selangor, Malaysia.

E mail:manohar@medic.upm.edu.my

Brunei Int Med J. 2013; 9 (6): 397-400

INTRODUCTION

Most cases of neuropathy involving

the LCNF are reported to be non-traumatic in

origin. 3–6 They are attributed to irritation of

the nerve from repetitive vigorous activity

where the nerve is fixed by the fascia and

compressed by the biceps tendon at its lateral

edge. 7 Iatrogenic injury of this nerve has also

been reported. 8 Venepuncture of the cephalic

vein may cause injury to this nerve because

of the close proximity of this nerve with ce-

phalic vein. 9, 10 Since this is nerve is purely

sensory and there is no motor deficit it may

be under-recognised. 9

CASE REPORT

A 50-year-old Indian housewife presented

with a 6-month history of discomfort involv-

ing the left forearm. There was no precipitat-

ing trauma or any invasive procedure carried

out that coincided or preceded with the

symptoms onset. She did not participate in

any sporting activity. However, she practices

yoga. She does not have diabetes mellitus or

any rheumatologic conditions also had or pri-

or history of these symptoms. The discom-

forts had gradually worsened over time. She

was only using a ketoprofen patch but this

did not ease her symptom.

On examination, there was sensory

deficit along the anterolateral border of the

forearm (Figures 1a and b). Otherwise, she

had no tenderness, no weakness and had full

range of motion. The rest of the neurological

and joint examinations were normal, and

there was no evidence of cervical spine prob-

lem. A nerve conduction study (NCS) showed

decreased sensory nerve action potential

(SNAP) of the LCNF (left 1.2 µV, right 3.3 µV)

(Figure 2). Needle electromyography (EMG)

was normal. Based on these findings, a diag-

nosis of sensory neuropathy of the left LCNF

was made based. She was referred for physi-

otherapy and showed a remarkable improve-

ment within six weeks. She is currently pain

free and showed complete resolution of her

symptoms

occurs because of compression of the LCNF

when women hang their handbag around the

elbow. Although relatively uncommon, the

possibility of entrapment of the lateral cuta-

neous nerve of the forearm must be consid-

ered as one of the differential diagnosis of

pain over the lateral aspect of the elbow. Pa-

tients, who presents with pain around the

elbow may manifest with paraesthesia along

the flexor aspect of the distal forearm. 1

Other causes of discomfort around

the elbow include lateral epicondylitis, cubital

tunnel syndrome, and radial tunnel syn-

drome. In lateral epicondylitis there will be

tenderness over the lateral epicondyle and is

usually aggravated by activities such as pour-

ing water from a kettle. Cubital tunnel syn-

drome is the compression of the ulnar nerve

at the elbow and usually there will be numb-

ness of the lateral one and a half digits that

are supplied by the ulnar nerve. Radial tunnel

syndrome is not that common and is caused

by compression of the posterior interosseous

nerve. There is however no muscle weakness

or numbness. It can be distinguished from

lateral epicondylitis, as the point of maximum

tenderness is about two to four centimetre

distal to the lateral epicondyle. In lateral epi-

condylitis, the tenderness is over the lateral

Figs. 1: a) The

area of discom-

fort on the dor-

sal aspect of

the forearm as

described by

the patient, and

b) the volar

aspect.

DISCUSSION

Entrapment of the LCNF at the elbow was first

described by Narasanagi 11 in 1972, and later

by Hale 12 as the ‘handbag paraesthesia’. It

AMURUGAM et al. Brunei Int Med J. 2013; 9 (6): 398

a b

epicondyle. On clinical examination, there

may be tenderness over this area, Tinel’s sign

maybe positive just lateral to the biceps ten-

don, dysaesthesia of the forearm in the an-

terolateral aspect and numbness of the lat-

eral aspect of the forearm. Symptoms are

usually worse with pronation against re-

sistance with the elbow in full extension. In

this position, the lateral border of the biceps

tendon may compress the nerve where it is

tethered at its exit point through the brachial

fascia. 13

Apart from lateral epicondylitis, cubi-

tal tunnel syndrome, and radial tunnel syn-

drome, other conditions that needs to be con-

sidered include cervical radiculopathy, brachi-

al plexus injury, and pronator teres syn-

dromes. 1 Our was examined for these vari-

ous conditions and was found to be normal.

Although she is 50 years of age, she did not

have any evidence of cervical spondylosis.

The presence of biceps weakness should alert

the examiner to the possibility of musculocu-

taneous nerve injury, or cervical radiculopa-

thy, as the lateral antebrachial cutaneous

nerve is purely a sensory nerve. 13 Only one

nerve was involved in our patient. If multiple

nerves are involved then the possibility of

polyneuropathy or viral brachial neuritis has

to be considered. Polyneuropathy involves

multiple nerves, whereas in viral brachial

neuritis different levels of the myotome and

dermatome are involved. Diagnosis depends

on detailed history, thorough physical exami-

nation, and good knowledge of anatomical

landmarks.

If in doubt, injections of local anaes-

thetic in the suspected area can discriminate

between lateral antebrachial cutaneous nerve

entrapment, lateral epicondylitis and radial

tunnel syndrome. 1, 14 It is diagnostic for radi-

al tunnel syndrome if patient develops tem-

porary posterior interosseous nerve palsy and

gets relieve from the pain. In addition, elec-

trodiagnostic studies (NCS and EMG) can be

helpful in confirming the diagnosis. The usual

finding of NCS is prolonged latency or de-

creased amplitude of the sensory NCS of the

LCNF in the affected side. 15

Treatment include resting and general

restriction, non-steroidal anti-inflammatory

drugs (NSAIDs), splinting, ultrasound stimu-

lation techniques, steroid injections locally

Figs. 2: Nerve conduction

study of lateral cutaneous

nerve of the forearm show-

ing reduced sensory ampli-

tude of the left lateral cuta-

neous nerve (b) of the fore-

arm compared to the right

side (a). a b

AMURUGAM et al. Brunei Int Med J. 2013; 9 (6): 399

and transcutaneous electrical nerve stimula-

tion (TENS). 1 Surgical exploration and de-

compression is usually recommended if con-

servative treatment fail after 12 weeks of tri-

al. 1, 7, 13, 14 A simple transverse incision cen-

tred over the point of maximal tenderness

along the anterolateral aspect of the lower

arm is usually made. The LCFN is then identi-

fied and released from the deep fascia. A tri-

angular wedge of aponeurosis overlying the

nerve is then resected to decompress the

nerve. 7, 13

Patients who present with parasthesia

usually require surgical intervention as

parasthesia represents a more progressive

stage of nerve entrapment. 15 Surgical treat-

ment in responder to conservative treatment

is simple yet effective in improving patients’

symptoms. 2, 15 Most will recover within a

month after surgery with almost complete

resolution of symptoms. 2, 7, 14, 15

In conclusion, entrapment neuropa-

thy of the LCNF should be considered in the

differential diagnosis of recurrent or chronic

elbow pain. Electrodiagnostic evaluation can

be very useful in establishing and confirming

diagnosis. If conservative treatment is not

effective in improving symptoms, surgical

decompression is recommended and it is as-

sociated with excellent results.

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